The first microscopes were rather primitive and allowed magnification of objects with little resolution.

History of Microscopy
http://www.microscopyu.com/museum/firstnikon.html

In the centuries since their initial development, microscopes have been drastically improved, and
our ability to both magnify and resolve objects has increased drastically.

Magnification and Resolving Power
http://www.biologymad.com/cells/microscopy.htm
http://nobelprize.org/physics/educational/microscopes/powerline/index.html
http://www.microscopyu.com/articles/formulas/formulasresolution.html
Here are some pointers about how to use a microscope.